Sunday, 20 August 2017

Spiders have been studied for centuries. In Middle English the name for spider was coppe and they built coppewebs, a word still retained in the language as cobweb. Yet despite our familiarity with these enigmatic air-breathing arthropods, scientists are still discovering new facts about them – and not necessarily about newly discovered species either. Here are ten amazing recently discovered facts about spiders.

10. Electrostatic Webs that Suck in Prey

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In 2013 students at the University of California, Berkeley, discovered that the web of the garden spider (or common cross spider) is attracted to charged objects. When a charged object is held next to a garden spider web, its threads arc towards each other. Many insects produce a charge when flying – the honeybee, for example, can generate a charge of up to 200 volts as it moves its wings. So, if one gets close to a web, the threads arc, effectively sucking the hapless creature in to the web.

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If you don’t already know, priapism is a condition where the penis can stay erect for hours. The genus Phoneutria commonly known as Brazilian wandering spiders (even though they are found elsewhere too) has a bite which can cause this condition which, unfortunately, is not harmless at all. In fact the erection the bite causes is very uncomfortable and in the worst cases can lead to permanent impotence.

However, all is not lost. The toxin which causes the problem, called Tx2-6, is currently being studied by scientists at the University of Georgia in the US. It is hoped that it may provide a breakthrough in the treatment of erectile dysfunction. In fact, researchers at the University of Wisconsin have discovered that the venom is indeed effective and has fewer side effects compared with erectile dysfunction drugs such as Viagra, which can cause a number of unpleasant side-effects .While this may not be good news for those who have already been bitten (and indeed those who will be in the future), it’s another reason why we should preserve as many species as possible – you never know whence a cure for something is going to come.

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Many female spiders eat their male paramour either during or after mating. While this may be nature’s way of supplementing the female’s diet while she produces, oviposits and protects her eggs the male of the orb web species has decided that he’d rather live a while longer.

The male spider’s sex organs are in its pedipalps (shortened to palp), the two ‘little legs’ you can see next to its eyes. Once he has inserted his into the female, the male snaps them off.

You may be wincing (particularly if you’re male) but this ensures not only survival but enables his sperm to keep pushing in to the female without any other male able to get his own palps anywhere near her. It also allows him to guard the female against any other approaching males, ensuring that his genes are carried on to the next generation. In fact, being palpless (that may not be a word found in the dictionary) makes him a better guard. Palps are heavy and without having to carry them around he has more stamina to ward off other males.

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Scientists at the University of Singapore have discovered that by snapping off their palps, male orb web spiders are not only lighter on their feet, the nine percent body weight reduction increases endurance by up to 80%.

Of course, many of them still get eaten by the female, with or without their palps. Survival of the swiftest.

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The male nursery web spider has another trick up his sleeve when it comes to reducing his chances of being eaten in flagrante. Researchers at the University of Nebraska have found that many males will attempt to tie up their mate so that she can’t grab and make a meal of him. Fortunately, the male nursery spider is large enough to attempt this daunting task.

The researchers discovered that the males that wrapped their silk around their prospective partner’s legs were seven times less likely to be eaten in way of gratitude for their desire to propagate the species. In order to do this, the team prevented some of their ‘volunteer’ males from initiating the silk spinning process (which seems a little unfair, frankly).

6. Two’s Company...Image Copyright Matthew Parsons
Oscar Wilde once said “Everything in the world is about sex except sex. Sex is about power.” Never a truer word spoken in jest but in the case of spiders, the power lies in being the one whose genes are passed on to the next generation. However, we have all been in situations where we feel it necessary to ask a friend to help us out.

Matthew Parsons, who teaches Biology and Ecology at Susquehanna University in Selinsgrove, Pennsylvania has discovered that the wolf spider does just that. Instead of weaving a web or snapping of his palp, some male wolf spiders approach females in pairs for a menage a trois. Parsons believes it is a ‘safety in numbers’ strategy to ensure that neither of the males gets eaten in pursuit of a little carnal knowledge. At first he believed this to be one-off behavior (he first spotted it, incredibly, in his back yard) but careful study showed it to be something that happens regularly.

Image Copyright Matthew Parsons
You might be thinking, with some pity, that one of the males will lose out, but fear not. The female wolf spider has paired reproductive organs. We’ll leave the rest to your imagination.

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We don’t associate spiders with vegetarianism but scientists at the University of Bern discovered that orb-weaving spiders (Araneidae) supplement their usual diet of insects with pollen. When they recycle their orb webs (in other words, ingest it in order to create a new one) the spiders also feed on fungal spores and pollen that has attached to their sticky webs.

This is done via extraoral digestion and that takes place by secretion of salivary enzymes onto the web (and attached vegetable matter), with the resulting liquid digestive products being sucked up by the spider. The scientists suggest that this is no accident – the pollen grains and other matter are too large for it to be so. As such, pollen can make up to 25% of the orb-weaving spider’s diet. As such it isn’t really a pure carnivore at all, as was previously believed.

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However, this is nothing compared to the ravishing Bagheera kiplingi, which is found in Central America and Mexico. Eric Olsen from Brandeis University discovered that its diet is almost completely vegetarian with the occasional ant larvae as a supplement. It eats the tips of acacia plants which are known as beltan bodies.

As a jumping spider, Bagheera kiplingi (yes, the name derives from The Jungle Book) is agile in the extreme and it has to be. The acacia has formed a symbiotic relationship with a species of ants who regard the beltan bodies as very much their property. However, Bagheera kiplingi hides from the ants in older leaves until it is hungry and then plays a dangerous game of sharks and minnows with the ants. Once it gets to a beltan body the spider snips it hurriedly off the leaf and then scrambles away to safety as fast as it can to enjoy its meal in peace.

Credit - First I is white
Researchers from Ball State University in Indiana spent a long time photographing the whitebanded crabspider (Misumenoides formosipes) to conclusively show how long it takes to change color from white to yellow and back again. And it takes a while.

The spider (the female but not the male which is, astonishingly, 20 times smaller) can go from white to yellow depending on the color of flower it has chosen as a base for ambushing prey. Interestingly, the scientists noted that when a yellow female was placed on a white flower she would quickly abandon it (despite the white flowers having a higher insect ‘hit rate’ than the white flowers at the university’s farm). Yet white females placed on a yellow flower would stay and change color to match.

Credit- Now I is yellow
The scientists believe that this means that morphing from white to yellow is less physiologically damaging than the reverse. And although this makes complete sense, the females who went from white to yellow on a yellow flower enjoyed an increase in prey capture, allowing the scientists to hypothesize that the color matching is more to do with deceiving prey than becoming it.

Credit - Then I haves me dinner
The scientists also discovered that the male whitebanded spider drinks nectar, which since this finding in 2015 has also been documented in a few other species.

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All spiders are venomous, right? Well, no. Cribellate orb weavers of the Uloboridae family are non-venomous. They have lost their venom glands. So, how do they kill their prey? The answer is that they crush it! Scientists from the University of Costa Rica observed the Philoponella vicina spider wrapping its prey extensively in up to several hundred meters of silk line. This has the desired crushing effect which kills the prey – the mouthparts of Philoponella vicina never touch its victim. Instead it spits digestive fluid all over the insect instead.

The process of ingesting starts almost straight away. The cuticle of the prey (which makes up most of the material of the exoskeleton of the insect) has been split open by the act of crushing, not to mention the digestive fluid. It’s an easy meal.

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You might ask how this particular spider avoids ingesting itself, what with all the slobbering going on. Its pedilaps are covered in particularly robust setae (stiff hair-like or bristle-like structures) which disallow this. As for the anterior legs (the ones nearer the front), Philoponella vicina cleverly spreads them out as far as it can to avoid becoming part of its own meal.

CreditAnelosimus studiosus (also known as the tangleweb spider) is a social spider and lives in colonies of up to 50 individuals. This allows the spiders to catch and share prey in a large collective web – food sources so large they could not possibly snare them on their own. The tanglewebs all look the same (not distinctive castes and bodies like ants) but some can be docile while others are much more aggressive.

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Research at the University of Pittsburgh has discovered that these ‘personality’ types dictate the jobs that separate spiders do ‘around the house’. For a while, however, they could not work out what the more docile spiders actually did – at first inspection it didn’t seem like anything in particular. Freeloaders? Going in to the wild, the researchers discovered that collective webs with both docile and aggressive members did much better than those with just one personality type.

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Lots of watching ensued. It turns out that the docile spiders were, in fact, the colony’s daycare workers. They spent their time guarding eggs or sitting protectively among groups of spiderlings. They were even seen to feed the young by a process of regurgitation. This allows the aggressive spiders more time to do things like build and strengthen the web, catch prey, and defend the colony from other species of spider on the graft.

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The dance moves of the Habronattus clypeatus (the jumping spider) were first recorded by natural historians over a hundred years ago. Yet what we didn’t know until recently is that the male of many species of jumping spider sings to its prospective mate. Damien Elias at Berkely was the first to hear these songs, using a modified phonograph needle to register the vibrations. Now it’s all done with lasers.

This is far from random noise. There are a number of motifs incorporated in to the spider’s song, each associated with its movements. Strangely, fit males sometimes end up as dinner while others that we might consider to have less potential are accepted. Permission to mate seems to be down to not just the dance but most definitely the song that the spider sings in accompaniment.

So, this song is evidently critical to success in the courtship process but it is not yet known exactly what it means to the female. Verse three is just amazing… Take a listen here!

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